Method of assembling a bearing

ABSTRACT

A flat, thin ring is formed into a modified ring having bridge material between adjacent, initial ball pockets. Movable anvils having a rounded surface are positioned within the initial ball pockets and the bridge material is flattened such that a flat bridge is formed between adjacent final ball pockets enclosing more than a 180 degree circumference of the rounded surface. The movable anvils are then moved such that the final ball pockets do not enclose more than a 180 degree circumference of the rounded surface to facilitate removal of the movable anvils from the final ball pockets. A method of assembling a ball bearing assembly is also described.

This is a continuation of application Ser. No. 08/189,955 filed Jan. 31,1994, now U.S. Pat. No. 5,404,642.

BACKGROUND OF THE INVENTION

This invention relates generally to ball bearing cages and, moreparticularly, to one-piece ball bearing cages that are installed in aball bearing assembly by "popping" or "snapping" over bearing balls.

One common type of ball bearing cage comprises two halves joinedtogether by welding, riveting or mechanical interlock. These two-pieceball bearing cages require insertion of the two halves from oppositeends of the ball bearing after the bearing balls have been loadedbetween the bearing rings. Welding is difficult due to potential arcingthrough the bearing balls, and riveting is difficult due to the manysmall rivets that must be inserted. Additional cost results frominspection and rejection of defective bearing assemblies.

Additional problems are associated with two-piece ball bearing cages dueto space requirements. Such ball bearing cages require sufficientcircumferential distance between bearing balls to permit welding,riveting or mechanical interlock of the two halves. As a result, fewerbearing balls may be inserted, reducing the load capacity of the bearingassembly. Also, when multiple rows of bearing balls are used, the rowsmust be separated to provide space for the ball bearing cages, adding tothe axial length of the bearing assembly.

Another type ball bearing cage comprises a sheet metal ring having aninitial undulatory configuration with open ball pockets spaced apart byU-shaped connecting portions. After being inserted between the bearingrings, with bearing balls placed in the pockets, the U-shaped connectingportions are upset, causing the sides of the connecting portions tospread and conform to the contour of the bearing balls. However, formingthe ball bearing cages directly against the bearing balls often resultsin excess gripping of the bearing balls or in insufficient ballretention.

Ball bearing cages may also employ a one-piece design having resilientfingers or lips which snap over the bearing balls as the bearing ballsenter the ball pockets to provide a simple pop-in assembly. Suchone-piece ball bearing cages are difficult to form of metal withsufficient ball contacting surface to retain the bearing balls. Moldedpolymer ball bearing cages of similar one-piece pop-in design mayprovide improved wrap-around and ball conformity. However, such polymerball bearing cages are limited to low temperature and low strengthapplications.

The foregoing illustrates limitations known to exist in present ballbearing cages. Thus, it is apparent that it would be advantageous toprovide an alternative directed to overcoming one or more of thelimitations set forth above. Accordingly, a suitable alternative isprovided including features more fully disclosed hereinafter.

SUMMARY OF THE INVENTION

In one aspect of the present invention, this is accomplished byproviding a method of forming a one-piece metallic ball bearing cage. Aflat, thin ring is formed into a modified ring having bridge materialbetween adjacent, initial ball pockets. Movable anvils having a roundedsurface are positioned within the initial ball pockets and the bridgematerial is flattened such that a flat bridge is formed between adjacentfinal ball pockets enclosing more than a 180 degree circumference of therounded surface. The movable anvils are then moved such that the finalball pockets do not enclose more than a 180 degree circumference of therounded surface to facilitate removal of the movable anvils from thefinal ball pockets.

In another aspect of the present invention, this is accomplished byproviding a method of assembling a ball bearing assembly.

The foregoing and other aspects will become apparent from the followingdetailed description of the invention when considered in conjunctionwith the accompanying drawing figures.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

FIG. 1 is a cross-sectional view illustrating tooling and a portion of apartially formed one-piece ball bearing cage of the present invention;

FIG. 2 is a cross-sectional view illustrating an alternative bridgeportion of a partially formed one-piece ball bearing cage of the presentinvention;

FIG. 3 is a sectional view along the line 3--3 of FIG. 1 illustratingthe tooling and a portion of the partially formed one-piece ball bearingcage;

FIG. 4 is a cross-sectional view illustrating tooling and a portion of afully formed one-piece ball bearing cage of the present invention;

FIG. 5 is a cross-sectional view similar to FIG. 4 illustrating asubsequent position of the tooling relative to the fully formedone-piece ball bearing cage;

FIG. 6 is a pictorial view illustrating the fully formed one-piece ballbearing cage of the present invention;

FIG. 7 is an elevational view, partially in section, illustrating apartially assembled ball bearing assembly and tooling for inserting theball bearing cage;

FIG. 8 is a side view, partially in section, of the partially assembledball bearing assembly and tooling of FIG. 7;

FIG. 9 is an elevational view illustrating a subsequent position of thepartially assembled ball bearing assembly and portions of the tooling ofFIG. 7;

FIG. 10 is an elevational view illustrating a subsequent position of thepartially assembled ball bearing assembly and tooling of FIG. 8; and

FIG. 11 is an elevation view similar to FIG. 7 illustrating a subsequentposition of the ball bearing assembly and tooling of the presentinvention.

Elements which are similar in the various embodiments of the presentinvention are indicated by the same reference numeral in the figures.

DETAILED DESCRIPTION

Referring now to the drawings, FIG. 1 illustrates a portion of apartially formed one-piece ball bearing cage 10 and tooling, comprisingmovable anvils 12, of the present invention that may be used to completea fully formed one-piece ball bearing cage.

To form partially formed ball bearing cage 10, a flat, thin ring ofmetal is first formed using any known forming method. For example, theflat ring may be stamped or punched as a "washer" from a wide strip ofsheet of flat metal. Alternatively, the flat ring may be formed from anarrow flat strip of metal which is coiled edgewise ("the hard way")into a split ring. The ends of the split ring may be joined by weldingor other means, with a butt, puzzle-cut or lap joint, coined to an eventhickness and trimmed to size to provide a uniform section.

Next, the flat, thin ring is modified into partially formed ball bearingcage 10 by forming initial ball pockets 14 and bridge material 16between adjacent, initial ball pockets 14. Conventional multistage diesor other means may be used to progressively gather the thin ring into anundulating configuration as the overall diameter of the ring is reduced.Subsequent die stages may progressively form initial ball pockets 14 andbridge material 16. Preferably, initial ball pockets 14 have aspherically concave bottom surface 18 to conform to a bearing ball;however, other concave configurations may be used with similar effect.

Side walls 20 and 22 of initial pocket portions 14 are not sphericallyconcave, thus facilitating use of conventional multi-stage dies. Bridgematerial 16 may include flat portions 24 and 26 providing a tent orpeaked configuration, as shown in FIG. 1, or may have rounded portion 28providing a curved arch configuration, as shown in FIG. 2. Flat portions24 and 26 or rounded portion 28 extend upward from side walls 20 and 22to provide sufficient material to form a desired bridge configuration ofthe finished ball bearing cage, as described below.

Movable anvils 12 are positioned within initial ball pockets 14.Preferably, rounded surface 30 of movable anvils 12 defines a band of asphere having a diameter slightly greater than that of the bearing ballswith which the finished ball bearing cage is to be used, to ensure thatthe bearing balls are freely rotatable. Rounded surface 30 is mounted onanvil post 32, which may be cylindrical. As shown in FIG. 3, movableanvils 12 include recessed side portions 34 that are recessed withrespect to spherical extension 35 of rounded surface 30 to provide anoverall "lollipop" shape. Recessed side portions 34 may be flat or maybe cylindrically curved, as shown, to conform to the bore and outsidediameter of the ball bearing cage.

As shown in FIG. 4, fully formed ball bearing cage 36 is formed byflattening bridge portion 16 (FIGS. 1 and 2) with suitable dies to formflat bridge 38 and to cause side walls 20 and 22 (FIGS. 1 and 2) to wraparound rounded portion 30, forming curved upper walls 40. Bridge ends 42and 44 are spread against anvil posts 32, which provide stop surfaceslimiting the length of flat bridge 38, ensuring that final ball pockets46 enclose more than a 180 degree circumference of rounded surface 30.As a result, final ball pockets 46 retain bearing balls both axially andradially with respect to the ball bearing cage.

Flattening of bridge portion 16 between initial ball pockets 14 (FIG. 1)thus creates a narrowed access to final ball pockets 46 to achieve thedesired retainment feature. The bore and outside diameter of partiallyformed ball bearing cage 10 (FIG. 1) are contained during this bridgeflattening operation in order to prevent radial growth or undesirabledistortion of the ball bearing cage. Anvil posts 32 provide a controlledclearance between bridge ends 42 and 44 of each final ball pocket 46 toensure that a desired amount of force is required to remove the bearingcage from a ball bearing assembly.

To facilitate removal of movable anvils 12 from fully formed ballbearing cage 36 without distorting the ball bearing cage, the anvils aremoved by rotation about axes perpendicular to the ball bearing cage orby another form of motion, for example, by tilting movable anvils 12,such that final ball pockets 46 no longer enclose more than a 180 degreecircumference of rounded surface 30 of movable anvils 12. Forillustrative purposes only, FIG. 5 shows movable anvils 12 rotated 90degrees relative to their position in FIG. 4; generally, a rotation of30 degrees is sufficient. The rotation of the anvils may be effected bya ring gear and pinions or by other known means.

FIG. 6 shows fully formed ball bearing cage 36 after removal of movableanvils 12. If the flat, thin ring is formed from a split ring, asdescribed above, weld joint 48 is preferably located in final ballpockets 46, as shown, rather than in flat bridge 38, to improveresistance to fatigue. At least one flat bridge 38 has predeterminedchordal length A, measured at pitch circle 50 of bearing balls 52, whichis greater than the space between adjacent bearing balls 52. As aresult, fully formed ball bearing cage 36 must be deformed to allowadjacent bearing balls 52 to pass between bridge ends 42 and 44 andenter final ball pockets 46.

The ball bearing cage may be formed of steel, brass, bronze or similarmetal. If a relatively soft material is used, the number of pressingstages required to form partially formed ball bearing cage 10 and fullyformed ball bearing cage 36 may be reduced. For example, initial ballpockets 14 of partially formed ball bearing cage 10 may have asimplified curved surface, and rounded portion 30 of movable anvils 12may serve as a die to form spherically concave bottom surface 18 inaddition to their function in forming flat bridge 38 and curved upperwalls 40.

Fully formed ball bearing cage 36 should have sufficient resiliency tosnap back to its fully formed configuration after being deformed duringinstallation of bearing balls 52 in final ball pockets 46, to provide apop-in installation. If the ball bearing cage is formed of mild steel,carburizing, hardening and tempering of fully formed ball bearing cage36 may be employed to create residual compressive stress and improveresiliency and fatigue resistance. Preferably, carburizing does notexceed one-third the thickness of the ball bearing cage and temperingensures that the surface of the cage is softer than the surface ofbearing balls 52.

FIGS. 7 and 8 illustrate tooling that may be used to insert fully formedball bearing cage 36 to complete a ball bearing assembly. Top plateshank 60 is mounted in a vertical press such that top plate 62 ismovable vertically, perpendicular to bearing end face 64 of ball bearing66, as shown by arrow B. Bearing balls 52 are within an annulus betweeninner and outer bearing rings 68 and 70 and are separated by an averagechordal distance less than the chordal length of at least one flatbridge 38. Ball bearing 66 may be the type with a wide inner bearingring 68 relative to outer bearing ring 70, as illustrated, or may be ofother configurations.

Pivot plate 72 is pivotably mounted on opposite sides of top plate 62 bymeans of trunnion blocks 74 and trunnion pins 76. Pivot plate 72includes stop bar 77 and stop washer 79 and is biased by compressionspring 78, or by other biasing means, against top plate 62 into theposition illustrated in FIG. 7. Loading punch 80 includes ring shapedshoulder 82 and is fixed to pivot plate 72 by clamps 84 at oppositesides of pivot plate 72. Center pilot 86 is fixed to top plate 62 andextends through bore 88 in loading punch 80 and a corresponding bore inpivot plate 72.

FIGS. 8 through 11 illustrate subsequent positions of the tooling andball bearing assembly of FIG. 7. The vertical press moves top plateshank 60, top plate 62 and center pilot 86 vertically, as a unit, suchthat center pilot 86 is advanced into bore 90 of inner bearing ring 68,as illustrated in FIG. 9 thereby maintaining proper alignment of ballbearing 66. Shoulder portion 92 of loading punch 80 then engages cageportion 94 as illustrated in FIG. 10, such that adjacent bearing balls52 move circumferentially, along pitch circle 50, allowing adjacent flatbridge 38 to pass between bearing balls 52 as the balls enter final ballpockets 46.

After this initial insertion of cage portion 94, further advancement ofthe tooling compresses compression spring 78 and pivots loading punch 80such that additional portions of fully formed ball bearing cage 36 arepressed downward against bearing balls 52. Bearing balls 52 movecircumferentially, along pitch circle 50, allowing the balls to enterthe remaining final ball pockets 46. Insertion is said to be"sequential" because bearing balls 52 do not all enter the ball pocketssimultaneously, that is, at least one bearing ball 52 (for example, abearing ball adjacent cage portion 94) precedes the others, which may ormay not enter simultaneously.

Although a simple pivoted loading punch is illustrated, having anabutment surface initially angled and subsequently parallel with respectto bearing end face 64, other types of tooling may be used to press theball bearing cage and force flat bridges 38 between adjacent bearingballs. For example, a V-shaped or curved abutment surface may be pressedagainst two cage portions to initially insert bearing balls 52 at thosetwo cage portions rather than at single cage portion 94. Ball bearingcage 36 may remain substantially as shown in FIG. 6 during insertion, ormay be temporarily bent to a "potato chip" configuration to facilitateinsertion over bearing balls 52.

Fully formed ball bearing cage 36 is made of a resilient material suchthat it returns to its fully formed configuration after bearing balls 52enter final ball pockets 46 to provide a pop-in assembly. Because atleast some of flat bridges 38 are longer than respective spaces betweenbearing balls 52, bridge ends 42 and 44 are engageable with bearingballs 52 to prevent ball bearing cage 36 from separating from bearingballs 52 in an axial direction with respect to ball bearing 66.Preferably, final bridge pockets 46 have a substantially sphericalconcave surface for receiving a circumferential portion of therespective bearing ball and have a slightly larger diameter to providefree rotation.

From the above description, it will be apparent that flattening ofbridge material 16 between and above the midpoint of open, loop-shapedinitial ball pockets 14 ensures that final ball pockets 46 have anarrowed opening to retain fully formed ball bearing cage 36. Movableanvils 12 provide a controlled interference fit with respect to bearingballs 52 during insertion and a controlled clearance after insertion ofball bearing cage 36 within ball bearing 66 to form a ball bearingassembly. Excess gripping of bearing balls 52 and insufficient retentionare thereby prevented.

The present invention provides a pop-in ball bearing cage havingimproved performance as well as reduced manufacturing cost. Becausejoining of cage halves is not required, costs and defects associatedwith welding and riveting halves are eliminated. Ball pockets may bemade closer together, allowing a greater number of bearing balls in abearing assembly of a given size, thereby increasing load capacity, andcloser spacing of rows of a two row ball bearing is permitted than withtwo-piece ball bearing cages. Better lubrication results from increasedspace for holding grease, and higher temperature applications arepossible than with polymer ball bearing cages.

Having described the invention, what is claimed is:
 1. A method ofassembling a ball bearing assembly, the method comprising the stepsof:forming a one-piece metallic ball bearing cage having an initialconfiguration with ball pockets and bridge portions between the ballpockets, at least a portion of the bridge portions having apredetermined chordal length; positioning bearing balls within anannulus between inner and outer bearing rings, the bearing balls beingseparated by an average chordal distance less than said predeterminedchordal length; and inserting the ball bearing cage into said annulussuch that circumferential movement of the bearing balls allows thebridge portions of the ball bearing cage to pass between adjacentbearing balls as the bearing balls sequentially enter the ball pockets.2. The method of assembling a ball bearing assembly according to claim1, wherein the ball bearing cage is made of a resilient material andwherein the step of inserting the ball bearing cage resiliently deformsthe ball bearing cage such that the ball bearing cage returns to saidinitial configuration after insertion.
 3. The method of assembling aball bearing assembly according to claim 1, wherein, after the step ofinserting the ball bearing cage, ends of at least a some of the bridgeportions are engageable with the bearing balls to prevent the ballbearing cage from separating from the bearing balls in an axialdirection with respect to the inner and outer bearing rings.
 4. Themethod of assembling a ball bearing assembly according to claim 1,wherein the ball pockets of the ball bearing cage each include asubstantially spherical concave surface for receiving a portion of therespective bearing ball, the concave surface having a diameter largerthan the diameter of the bearing ball such that the bearing ball mayfreely rotate within the ball pocket.
 5. The method of assembling a ballbearing assembly according to claim 4, wherein the concave sphericalsurface subtends an arc of more than 180 degrees to retain the bearingball within the ball bearing cage.
 6. The method of assembling a ballbearing assembly according to claim 1, wherein the step of inserting theball bearing cage into the annulus between the inner and outer bearingrings comprises forcing a first bridge portion between adjacent bearingballs and subsequently moving the ball bearing cage such that otherbridge portions are forced, sequentially, between other adjacent bearingballs.